Power brake valve



NOV- l 1955 F. w. scHNl-:CK 2,722,233

P@ 911:' VALVE Filed April a. 1952 mmvmx. E W. Schneck y ATTORNEY limited States Patent Ofce POWER BRAKE VALVE Frederick W. Schneck, Northridge, Calif., assignor to Bendix Aviation Corporation, North Hollywood, Calif., a corporation of Delaware Application April 8, 1952, Serial No. 281,145

3 Claims. (Cl. 137-620) This invention relates to pressure-reducing valves for controlling the application of pressure fluid to hydraulic brakes and like hydraulic devices.

An object of the invention is to provide a simple valve in which opening movement is unopposed by the pressure of the source and closing movement positively insures release of pressure in the brakes.

A feature of the invention is a pressure-reducing valve having a slide valve element controlling flow of fluid from the high pressure source to the load and a poppet valve element controlling release of fluid from the load.

Other more specific objects and features of the invention will become apparent from the description to follow.

Heretofore power brake valves have been either of the slide valve type or poppet valve type. valve type has the advantage over the poppet type that there is less resistance to opening movement, but has the disadvantage that it may stick open because of dirt lodging between the closely fitted surfaces. Sticking in the prior slide valves could produce excessive pressure in the brake line and lock the brakes, a dangerous condition. Because of this danger it has been considered necessary by some users to provide a separate relief valve in the brake line to prevent excessive pressure being created.

The present 'invention' provides a poppet return valve in combination with a slide type pressure inlet valve. The poppet return valve is always free to open in response to excess pressure, thereby giving the protection against excessive pressure aiforded by a full poppet type valve, but retaining the easy operating characteristics of the slide type valve.

A full understanding of the invention may be had from the following detailed description of a preferred embodiment thereof as illustrated in the single figure of the drawing.

Referring to the drawing, there is shown a valve casing having a working or delivery port 11, a high pressure port 12, a return port 13 and a control port 14. Normally the delivery port 11 is connected to the return port 13 so that no pressure exists therein. However, in

response to a control pressure appliedvto the port 14, valve elements within the casing are actuated to disconnect the delivery port 11 from the return port 13 and connect it to the pressure port 12. The valve functions to admit pressure uid from the pressure port 12 to the delivery port 11 to the extent necessary to develop in the delivery port a pressure that is higher than but proportional to the control pressure in the port 14. When the control pressure in port 14 is reduced, the valve functions to disconnect the delivery port 11 from the pressure port 12, and connect it to the return port 13 to the extent necessary to reduce the delivery port pressure to a value proportionate to the control pressure in the control port 14.

The casing 10 comprises a main body 16 having a cylindrical bore 17 therein in which is fitted a liner 19 The slide n having a bore 19a which constitutes a valve cylinder. The liner 19 contains a high pressure chamber 20communicating with the valve cylinder 19a and with the pressure port 12. The liner 19 is provided with sealing rings 22, 22 on opposite sides of the pressure chamber 20 to prevent leakage of fluid between the liner and the body bore 17. An end cap 23 closes the right end of the body bore 17 and is provided with a sealing ring 24 to prevent leakage of pressure Huid past the outer end of the liner 19. Rearwardly (to the left) of the liner 19 to the bore 17 is in communication with the return port 13.

Closely but slidably fitted in the valve cylinder 19a is a valve sleeve 26 having a` central passage 26a extending therethrough and having lateral passages 26b which are normally disposed to the rear of and disconnected from the pressure chamber 20. The sleeve 26 is normally retained in rear (normal) position by a helical compression spring 29 compressed between the end cap 23 and the inner end of a counterbore 26C in the forward end of the sleeve 26, the rearward movement of the sleeve by the spring being limited by a snap ring 26d, positioned in an annular groove on the sleeve 26, which engages the-inner end of a counterbore 19C in the liner 19.

The rear end of the valve sleeve 26 is enlarged and provided with a counterbore 26f of the same diameter as the cylinder 19a, the outer end of this counterbore constituting a poppet seat for a ball poppet 30.

For convenience in manufacture, the poppet seat 26g may be defined by a separate sleeve 45 positioned on a reduced rear end section of the sleeve 26 and sealed with respect thereto by a sealing ring 47.

The poppet 3i) is normally supported in slightly spaced relation with respect to the poppet seat 26g by a pusher member 31 which is guided for sliding movement in the bore 17 of the body 16. The ball poppet 30 is actually contacted by the head 32a of a bolt 32 which extends through the member 31 for a purpose to be described later, but this is merely incidental. The pusher member 31 is yieldably urged to the left by a light compression spring 34 which is compressed between the end of the liner 19 and the pusher member 31.

The body 16 is provided with a rearward extension 16a on which there is threaded a tubular housing 35 which defines a control cylinder 35a containing a control piston 36. The rear Vend of the housing 35 is closed by a plug 37 which contains the control pressure port 14.

The piston 36 has an annular shoulder 36a against which there rests a disc 39 which is coupled to the poppet pusher member 31 by a helical compression spring 40 which is compressed between the disc 39 and the pusher member 31. This spring 40 is preloaded by the bolt 32 which, as previously described, is connected at its right end to the pusher member 31, andextends through an aperture provided therefor in the disc 39 andhas a nut 32b anda lock nut 32con its rear end, for limiting separating movement of the pusher member 31 and the dis'c member 39. By adjusting the nuts 32b and 32C the spring 40 can be preloaded to any desirable extent, to balance the combined forces of the springs 34 and 29.

The maximum desired loading of the spring 40 is adjusted by rotating the member 35 on its threaded connection with the body extension 16a. Thereafter, the spacing between the poppet 30 and the poppet seat 26g is adjusted by adjusting the position of the end cap 37 in the member 35.

The valve operates as follows:

With the elements in normal position as shown in the drawing, the high pressure port 12 is disconnected from the delivery port 11 by displacement of the valve sleeve ports 2Gb rearwardly from the pressure port 20, and the delivery port 11 is connected through the passage 26a in Patented Nov. 1, 1955 the valve sleeve 26, past the poppet 30, to the chamber 48 which is always in communication with the return port 13. Now let it be assumed that pressure uid is admitted to the control port 14 to shift the piston 36 therein to the right. This movement is transmitted through the preloaded spring 40 to the poppet pusher member 31 which pushes the poppet 30 into engagement with the seat 26g. Thereafter, continuing movement of the piston 36 carries the valve sleeve 36 with it until the ports 2617 register with the pressure chamber 20, permitting liow of high pressure fluid through the ports 2Gb and the passage 26a to the delivery port 11.

The pressure in the delivery port 11 is always applied to the poppet 3() when the latter is closed against the seat 26g, producing a reactive force on the poppet which is transmitted through the poppet pusher 31 and the spring 40 to the piston 36, thereby apprising the operator, by the reaction pressure created within the control port 14, of the pressure that has been applied to the brakes. Whenever-the reaction pressure exceeds the force of the spring 40, the poppet 30 and the pusher 31 are moved to the left by it. The sleeve 26 follows the poppet because of the constant force exerted thereon by the spring 29. A relatively slight movement of the sleeve 26 to the left disconnects the ports 26b from the pressure chamber 20, thereby isolating the delivery port 11 from the pressure source. After leftward movement of the sleeve 26 is limited by engagment of the snap ring 26d with the counterbore in the liner 19, the poppet 30 then leaves the seat 26g, to permit the pressure fluid in the delivery port 11 to be exhausted into the chamber 48 and thence out through the return port 13.

It will be noted that even if, as a result of dirt in the uid, the sleeve 26 should stick in forward position in which the ports 26b are connected to the pressure r' chamber 20, the pressure within the delivery port 11 will be relieved at any time the poppet pusher 31 is retracted, because the pressure will always force the poppet 30 away from the seat 26g and permit relief of the pressure within the passage 26a to the return port 13.

As has been previously described, the diameter of the seat 26g is substantially the same as the outside diameter of the portion of the sleeve 26 seating in the cylinder 19a. Hence when the poppet 30 is engaged with the seat 26g the opposite end areas of the sleeve 26 exposed to the high pressure Huid in the delivery port 11 are equal and opposite so that there is no resultant pressure thrust on the sleeve in either direction. This is desirable for the reason that it leaves the sleeve balanced by the pressure forces and permits the opening of the poppet 30 by the pressure thereagainst promptly in response to retraction of the control piston 36. If the seat 26g were smaller than the cylinder 19a, additional leftward movement of the piston 36 would be required to open the poppet 30 after completion of leftward movement of the sleeve 26.

It is to be understood that the invention is not limited to a pressure-reducing valve in which the controlling force is derived from a master cylinder, but is equally applicable to systems in which the controlling force is applied directly to the disc 39 or the pusher 31.

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur t0 a person skilled in the art, and I do not desire to be limited to the exact details shown and described.

l claim:

l. A valve comprising: a casing having a pressure port, a delivery port and a return port; a valve cylinder in said casing having a lateral pressure chamber connected to said pressure port, a forward end spaced from said pressure chamberand connected to said delivery port, and a rear end spaced from said pressure chamber and connected to said return port; a valve sleeve reciprocable in said cylinder in sealing relation therewith and having an axial passage extending therethrough, said sleeve having a poppet seat at its rear end and a lateral port extending through said sleeve from said axial passage and registering with said pressure chamber in an advanced position of said sleeve and displaced from said pressure chamber in a normal retracted position of said sleeve; a poppet at the rear end of said sleeve movable against said poppet seat to break communication between said return port and the said axial passage in said sleeve and advance said sleeve; and actuating means for moving said poppet; said cylinder and valve sleeve having cooperating, closely-fitted sliding surfaces sealing with each other on each side of said pressure chamber in all positions of said sleeve whereby said lateral port and axial passage in said sleeve constitute the sole ow path for iiuid between said pressure chamber and said delivery port.

2. A valve according to claim 1 in which said sleeve projects rearwardly beyond said valve cylinder and has a rear end portion the external diameter of which is larger than said cylinder, said rear end portion having a counterbore of substantially the same diameter as said cylinder and defining said poppet seat.

3. A valve according to claim l in which said actuating means comprises: a poppet pusher member engaging the rear end of said poppet and means guiding it for sliding longitudinal movement in said casing; an actuating member rearwardly spaced from said pusher member and means guiding it for longitudinal movement; a helical compression spring interposed between said pusher and actuating members for yieldably coupling them; and spring preloading means comprising an axial rod extending through apertures provided therefor in said members and having heads on its outer ends engaging said members for limiting separating movement of said members, one of said heads including a nut means threaded on said rod for varying the effective length of the rod to adjust the preloading of the spring.

References Cited in the tile of this patent UNITED STATES PATENTS 1,727,970 Doty Sept. 10, 1929 2,375,110 Hufford May l, 1945 2,513,486 Herman July 4, 1950 

